Eric,
From my limited knowledge of metallurgy, raw aluminum immediately bonds with oxygen in the air forming a self-protecting coat of aluminum oxide. It's hardly protective however...
I would suspect that your paint had pinholes in it; the pinholes let foreign substances in which reacted with the aluminum, and you began to get the same kind of effect you can sometimes see on aluminum wheels--where the corrosion or oxidation or galvanic disturbance (whatever you choose to call it) is spreading under the paint. Sometimes you can see this on a clear-coat wheel; a little scratch lets in the bad stuff, and you get this growth underneath the clear coat that gets bad to the point where it might flake off.
I assume since you removed the paint yourself, you will be painting it yourself. If that's that case, your paint supplier will have the proper support through the manufacturer to provide you with the right products. It is a bit different than painting steel; to do it right you have these various preps to de-oxidize, and specialty primers.
I suggest choosing your paint, and calling the manufacturer's tech support to get the right product mix and process. You don't want to do it again.
If you are so inclined, find the Jaguar dealer in your area; ask them who is certified for repair/paint on their aluminum cars (not too many are!) and have a chat; I'm sure they would be friendly enough to tell you what they use.
